There are several sports in which a ball is struck by a player using his or her hands or feet, with or without the aid of a tool such as a bat or club.
Most often, part of a player's skill is to hit or kick the ball not only at a desired moment, and with a desired forcefulness, but also in a desired direction (i.e., so as to have its trajectory as projected onto a horizontal surface, usually the ground plane, have a particular angle, about a vertical axis, relative to a datum direction along the horizontal surface).
It is not surprising, then, that players seek to develop their skills, including their skill of directionality of projection of a hit or struck ball.
Typical are the players who hit balls by the bucket at driving ranges and football players who spend hours practicing place kicking, punting, drop kicking and the like.
A well-recognized by-product of such practice is balls to be retrieved. The by-product does not present a problem when the player has a cooperative relationship with another person, such as in football practice, when a second payer, cooperating with the first, can be practicing catching and running. But there are times and instances in which ia cooperative relationship is not available, or is only available at an unacceptable cost, such as when a practicer of golf might not be able to afford to pay another person to retrieve the hit balls, or may not have a sufficiently large supply of balls to hit, necessitating frequent interruptions for ball retrieval.
One conventional solution to such problems is the provision of a net, often one with a target painted on it or otherwise provided in relation to it. The net is placed much closer to player than the ball would otherwise travel when hit or kicked. Accordingly, the time and effort needed for ball retrieval, and the stock of balls needed for carrying out a reasonably-paced practice session are all reduced.
The net-type target concept is a good one, but a player may have difficulty remembering, after the ball has struck the net and fallen to the ground just where the ball did hit.
The addition of mechanical or electronic sensors in connection with the net for giving the player a lasting indication of the trajectory of the ball, and particularly where it struck the target are elaborations which only increase the bulk and expense of an already generally large and expensive accessory to the practice session.